Astrologian guide...?

[Lyrica_Ashtine]

The things I want to know are the best card use and when / how to use Nocturnal properly. That's it.

I'll give you a more compact version of the cartomancy guide I wrote on my FC's forum:
Know the theoretical value of each card you can play in any combination (for example: 10% balance on a melee is not a 10% dps increase)
Define ABC encounter (Attrition, Burst and Coffee break encounters). The value of each card fluctuates according to the type of encounter.
Keep an eye on your party's resources, not just your own - No one likes an Astrologian slapping an Ewer on themself when you're at 10k MP and your co-healer is at 1k

Don't assume certain cards are fodder by default - A summoner/Scholar will thank you for a well timed Spear.
Don't use that silly flowchart in another topic somewhere in the healer forum

As for "how to use Nocturnal Sect". There are plenty of ways to approach this. My personal style for this is to use Aspected Benefic as a snipe-healing tool, like how you'd use Essential Dignity, Lustrate and Tetragrammaton. It's still 262 potency worth of healing and 341 potency worth of shielding, combined 603 potency. It's especially useful for those stray DPS players who like to keep their range to a maximum for no reason and stay out of AoE healing range. You'll notice this specific behaviour in The Aery and The Vault. Additionally you might want to consider off-DPSing when in Nocturnal stance as well; Aspected Benefic the key targets -> Cleric's Stance -> DPS a bit -> Cleric's off -> Essential Dignity -> Aspected Benefic -> Cleric's Stance etc.